Heat Illness: Risk, Treatment, Prevention

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Heat IllnessRisk, Treatment, Prevention

• Terence Lonergan, Maj., USAF, MC
• Flight Surgeon
• Wright State University
• Department of Emergency Medicine

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Overview

• Normal Control of Body Temperature
• Acclimation to Hot Environments
• Types of Heat Illness
• Treatment
• Prevention

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Normal Control of Body Temp.

• Normal body temp about 37 C (98 F)
• Human bodies constantly generate heat
• In cool environments lose heat easily
• The hotter it gets
• Increased blood flow to skin
• Sweating starts (evaporation), up to 1.5 L/hr
• Sweating depletes water and salt
• Thirst starts once you are already dehydrated

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Acclimation

• Adaptation to a hot environment
• Takes about 2 weeks
• Actually sweat more, but lose less salt
• The body produces less heat

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Heat Illness

• Occurs when heat produced gt heat lost, over time
• Victims are not always dehydrated
• Can range from mild symptoms to a true medical
  emergency
• Several distinct types are seen

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Heat Syncope

• Usually someone who is in poor shape
• Body sends lots of blood to the skin
• Not enough blood is left to flow to the brain
• They faint
• They recover quickly

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Heat Cramps

• Painful spasms in arms, legs, abdominals
• Usually after several hours of exertion with
  large volumes of sweat
• Caused by depletion of salt, not water
• More likely in fit, acclimated people

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Heat Exhaustion

• Usually a deconditioned person
• Inability to continue activity
• Might collapse, might be mildly confused
• Other symptoms
• dizziness, nausea, vomiting, muscle cramps

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Heatstroke

• True medical emergency, 90 survive
• Classic type
• Elderly, very young, or chronically ill
• Simply overwhelmed by outside heat source
• Exertional type
• Outside heat inside heat production
• Usually still sweating

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Heatstroke (cont.)

• Usually there is physical collapse
• Temperature gt 40.5 C (105 F)
• Very confused or comatose
• Requires immediate medical attention

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Treatment of Heat Illness

• Heat cramps, syncope, exhaustion
• Stop activity, get to shade
• Remove restrictive clothing as appropriate
• Cool them down ice, wet towels, water
• Start drinking, 1-2 liters over 2-4 hours
• No return to activity that day
• - Heatstroke requires cooling and emergency
  medical care

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Prevention

• Know your level of acclimation, fitness
• Modify activity according to temp. and humidity
  early AM and late afternoon best
• Drink before, during, and after
• You will not be as thirsty as you need to be
• Monitor urine color, clear or light yellow
• Use sun protection

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Heat IllnessTake Home Points

• Occurs in anybody when cooling isnt adequate
• Must be aware of your fitness, level of
  acclimation
• Drink early, often you wont be thirsty enough
• Modify activity (time of day, length, intensity)

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Heat IllnessTake Home Points

• Treat heat illness by drinking, cooling down
• Heatstroke is an emergency that requires medical
  treatment

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Hypothermia and Cold Injury
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Chilblain

• Definition mild but uncomfortable inflammatory
  lesions of bare skin from chronic exposure to
  damp, nonfreezing conditions precipitated by
  acute exposure
• Symptoms swelling, redness /or cyanosis,
  plaques, nodules, burning pain and itching.
• Treatment supportive, gently rewarmed, bandaged,
  and elevated

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Chilblain
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Trench Foot (immersion foot)

• Definition direct injury to soft tissue caused
  from sustained and prolonged cooling,
  particularly in damp/wet environments
• Symptoms reversible tingling to irreversible
  numbness foot is pale, mottled, pulseless, numb,
  immobile. Severe burning pain after rewarming.
• Treatment Supportive -- keep yourself warm, keep
  feet dry, don't wear/sleep in wet socks/boots.

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Trench Foot (immersion foot)
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Frostnip Frostbite

• Definition shutting down of all blood flow to
  the coldest extremity leading to ice formation
  (freezing) in the tissue and potentially
  irreversible damage.
• Symptoms varies depending of severity from
  swelling and redness to deep, aching, throbbing
  pain, blisters, eschar formation, and loss of
  limb
• Treatment see following slides

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Frostnip Frostbite
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Frostnip
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Beck Weathers, MDMount Everest, 1996
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Frostbite Treatment

• Remove patient from environment and get to ER
• Remove wet, constrictive clothing. Wrap in dry,
  sterile gauze with fingers/toes separated and
  avoid further injury!
• Aggressive wound management should be avoided!
• However...

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Frostbite Treatment

• If one should attempt field treatment
• 1. Rapid rewarming in measured 104-108 degrees F
  clean water for 10-30 min, or until tissue is
  pliable
• ONLY IF THERE IS NO CHANCE OF REFREEZING!
• Don't use dry heat (fires,heaters) -- tend to
  damage tissue
• 2. Remove clear blisters and cover with aloe vera
  and dry, sterile bandages -- leave blood blisters
  intact
• 3. Pain management Ibuprofen _at_ 12mg/kg/day in
  addition to narcotics -- don't smoke!
• 4. Infection?? Tetanus??

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Hypothermia

• 1. Definition Core body temperature of less than
  95 degrees F
• 2. How do we lose heat?
• Radiation, convection, conduction, evaporation
• 3. Can lose heat even in moderate climates.

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Hypothermia -- stages
98 - 95 degrees - Sensation of chilliness, skin
numbness minor impairment in muscular
performance, especially in use of hands
shivering begins. 95 - 93 degrees - More obvious
muscle incoordination and weakness slow
stumbling pace mild confusion and apathy. Skin
pale and cold to touch. 93 - 90 degrees - Gross
muscular incoordination with frequent stumbling
and falling and inability to use hands mental
sluggishness with slow thought and speech. 90 -
86 degrees - Cessation of shivering severe
muscular incoordination with stiffness and
inability to walk or stand incoherence,
confusion, irrationality. 86 - 82 degrees -
Severe muscular rigidity patient barely
arousable dilatation of pupils unapparent
heartbeat and pulse. Skin ice cold. 82- 78
degrees and below - Unconsciousness death due to
cessation of heart action.
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Hypothermia Treatment -- mild

• Protection, external warming, central warming
• Protection Move him/her out of environment and
  into warmer location (tent, shelter, snow cave,
  lodge, car)
• External warming dry clothing (good insulating
  clothes), insulate from ground with
  mat/leaves/grass, build fire, hot water
  bottles/stones in groin/neck/ armpits, put in
  sleeping bag with someone else, boil lots of
  water to humidify air.
• Central warming difficult in field -- hot drinks
  (don't burn person!), boil water to humidify air,
  warmed IV fluids, warm gastric/bladder/peritoneal/
  thoracic lavage, careful of rebound hypothermia
  and acidosis -- don't warm extremities first!

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Hypothermia treatment
Severe hypothermia is difficult to treat without
specialized equipment -- must be prepared to
spend potentially hours to days since you can't
move patient secondary to fatal heart
arrhythmias! Of course, the best treatment is
PREVENTION! EAT, DRINK, DRESS PROPERLY!!
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Back to BasicsHow to Dress Yourself!

• 1. Base Layer wicking material that is against
  skin
• Example polypropylene, Thermax, Coolmax,
  Capilene
• 2. Insulating layer what is keeping your heat
  in!
• Example wool, fleece, pile, down
• 3. Outer layer protection from
• elements
• Usually wind/water proof
• Examples Gore-Tex, Conduit,
• Membrane, Hy-vent, Omni-tech

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Questions?